Neutrino Mass Matrix Related to Up-Quark Masses and Nearly Tribimaximal Mixing -- Based on a Yukawaon model --

Based on a new approach (the so-called Yukawaon model) to the mass spectra and mixings, a neutrino mass matrix which is described in terms of the up-quark masses and CKM matrix parameters is proposed. The mass matrix successfully leads to a nearly tribimaximal mixing without assuming any discrete symmetry.